Raney copper catalysts are conventionally prepared by contacting a starting copper aluminum alloy in particulate form with aqueous alkali metal hydroxide to remove some portion of the aluminum present initially. The manner in which such contacting is conducted affects the properties of the resulting Raney copper catalyst in such reactions, for example, as the hydrolysis of acrylonitrile to acrylamide under aqueous liquid phase conditions conducted in the presence of such catalyst.
Apparently, Raney copper catalysts have heretofore always been prepared with attention being given primarily to aluminum removal. Apparently complete aluminum removal was heretofore sometimes believed to have been achieved and to be desirable for purposes of enhancing catalyst activity for this nitrile hydrolysis reaction; see, for example, Canadian Pat. No. 899,380, at p. 5, where the Kawaken Fine Chemicals Co. Raney copper catalyst is used. According to Kawaken Fine Chemical Co. trade literature, it appears that substantially complete aluminum removal is achieved in such catalyst.
The art theorizes that Raney catalysts can contain amounts of insoluble aluminates which are sufficient to adversely affect catalyst activity and life for whatever reason, and the art has described processing procedures alleged to remove such impurities; see for example, U.S. Pats. Nos. 2,673,189; 2,604,455; 2,950,260; and British Pat. Nos. 642,861 and 658,863.
It has heretofore been proposed to activate Raney alloys for use as fuel cell electrodes by using in the activating solution alkali metal tartrates or polycarbonxylates aliphatic amino compounds; see U.S. Pat. No. 3,235,513. See also U.S. Pat. No. 3,067,276 for a discussion of catalyst regeneration using citric acid.
Because of the limitations and short-comings observed for prior art Raney copper catalysts as respects catalyst initial activity and catalyst life, the art continues to seek improved Raney copper catalysts such as will be particularly suitable for use in such a nitrile hydrolysis reaction operated, for example, at rapid conversion rates and high conversion levels using a concentrated acrylonitrile/water feed.
So far as is known, no one has ever heretofore used gluconic acid and closely related materials in preparing a Raney copper catalyst. For one thing, the prior art teachings above indicated would clearly lead those skilled in the art away from this type of material. Thus, when the tricarboxylic hydroxylated citric acid and the dicarboxylic hydroxylated tartaric acid are each used to activate a Raney copper catalyst with caustic and the product catalyst is then evaluated for activity in the catalytic hydrolysis of acrylonitrile to acrylamide, it is found that the tricarboxylic citric acid is somewhat more effective in increasing catalyst initial activity over the caustic conventionally activated catalyst than is the dicarboxylic tartaric acid which leads to the tentative hypothesis that increase in degree of carboxylation in an additive promotes catalyst initial activity. This hypothesis would appear to be strengthened by the added fact that monocarboxylic hydroxylated acids when similarly evaluated as additives to promote Raney copper catalyst activity display little or no effectiveness over the use of aqueous caustic employed above for catalyst activation when evaluated for activity in the same catalytic hydrolysis of acrylonitrile to acrylamide.
Thus, lactic and glycolic acids offer no advantage or particular value as additives for activation with alkali metal hydroxide of a Raney copper catalyst. On the other hand, if hydroxylation is a key to additive effectiveness in promoting such desired good initial Raney copper catalyst activity (in such a catalyzed nitrile conversion) then such prior art still fails to teach or suggest this type of material. Glycolic and lactic all are monohydroxylated acids. While tartaric acid is dihydroxylated, it displays less activity as an additive used for catalyst promotion than does, for example, citric acid. Furthermore, even a tetrahydroxylated compound like pentaerythritol, when similarly evaluated as an additive for a Raney copper catalyst and the product catalyst used for such nitrile hydrolysis, displays inferior activation additive value compared to gluconic acid and materials closely related thereto.
Nothing in the prior art teaches or suggest gluconate type materials for use in alkali metal hydroxide activation of Raney copper catalysts.